You can use the Trizol (phenol-chloroform) extraction method to extract RNA. I currently use the Qiagen PAXgene Blood kit. I am yet to test if there are any differences in terms of yield between the two methods. So far the selection really depends on the amount of extractions you have to do. The PaxGene allows you to use automated systems (although you can do it manually as well) such as QiaCUBE).
If you are handling few samples, manual Trizol extraction should do the job.

The RNAeasy kits of Qiagen are all based on the Boom et al., extraction procedure of 1990. This is the fastest, most efficient way to purify RNA. You can modify these procedures by fractionating nuclei and cytoplasm to give only nuclear or only cytoplasmic. Here is the Boom paper: http://www.ncbi.nlm.nih.gov/pubmed/1691208
One Qiagen kit is called RNAeasy Protect Animal Blood Kit. Search for it in google. Good luck.

Well you need to first isolate WBC's by layering Blood on top of Ficoll gradient in 1:1 ratio, to get get of other cell types by centrifugation at 1500xg for 15 min. Seperate white band (WBC's) from the gradient and wash with serum contaning MEM by pelleting by centrifugation, which eliminate platelets, wash pellet with serum free MEM followed by PBS twice with quick centrifugations. Once you get WBC's pellet you can either use TRIzol or Qiagen RNAeasy kit to purify the RNA. I hope this helps

I had very good results with the method described by Puissant and Houdebine (1990) published in BioTechniques, 8:148-149. That method (method 3 in the paper) is appropriate for large-scale total RNA preparation and it has a high yield. The protocol is described step by step, but you have to read also the paper of Chomczynski and Sacchi (1987) Analitical Biochemistry 162:156-159 for details of preparation of denaturing solution and the chloroform-isoamylalcohol mixture. Other methods for RNA isolation with reagents like trizol are simpler procedures, but with less yield and more suitable, in my opinion, for small-scale RNA preparation. Working with RNA is a very laborious procedure because RNA is an extremely “labile” molecule, prone to be degraded by RNase and in order to preserve its integrity the conditions in reactions must be free of the action of these enzymes. These require a careful preparation of the material and solutions to be used for RNA isolation, so I recommend to read some literature that introduce you to the methods that will allow you to succeed in RNA preparation.